Vacuum-pump



l S. H. HALL.'A VACUUM PUMP. APPLICATION FILED FEB. 3. |920;v

Patented Apr. 12, 1921.

'arrancan S. H. HALL; VACUUM PUMP.

APPLICATION FILED'FEB. 3, 1920.

Patented Apr. 12, 1921.

`'Z SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

sELDEN H. HALL, or POUGHKEEPSIE, NEWv YORK, AssIGNoR rro THE DE LAVALsEPAaA'rOR COMPANY, or NEW YORK, N. Y.,'A CORPORATION OF NEW JERSEY,

VACUUM-PUMP.

Specification of Letters Patent. Patented Apr. 12, 1921.

Application iiled February 3, 1920. Serial No. 355,999.

To all whom t may concern Be it -known that I, SELDEN H. HALL, a citizenof the United States,-residing at Poughkeepsie, county of Dutchess, andState of New York, have invented a new and useful Improvement inVacuum-Pumps, of which the following is a full, clear, and exactdescription, reference being had to the accompanying drawings, whichform a part of this specification.

My invention relates to pumps of the known type having an approximatelycylindrical body in which there is eocentrically mounted a rotorcarryingvanes adapted to slide outward and press against the inside ofthe body. The body, in well designed pumps of this type, varies from thecylindrical form enough to cause all chords drawn through the center ofrotation of the rotor to be equal.

In order that this type of pump may run easily, appreciablel clearancesmust be left between the rotor and the body, between the ends of thevanes and the heads, and in the rotor at the sides of the vanes.Frequently a considerable quantity of oil is used to seal theseclearances.

Many of these pumps are used in the operation of cow milking machines.In such cases the inlet to the pump is always at about half ofatmospheric pressure (about 15-16 inches of vacuum) and the discharge isat atmospheric pressure.

Pumps of the general construction above specified exhibit three notablefaults. First,l the discharge is very noisy; second, the discharged aircarries with it a large quantity of oil in such a finely divided statethat it is impossible to catch it in an oil separator;v

and third, the efficiency is low.

I have found that all three faults inoperation are due to one error inconstruction, namely: that the ports between the com- I pressing chamberand the discharge passage are allowed to open before the pressure 1n thecompressing chamber is equal to that in the discharge passage. Theresult is that at every opening of the port there is a rush of air fromthe discharge passage into the compressing chamber and then, as the vanemoves forward, this air, in addition to that drawn in at the suctioninlet, has to be forced out through the discharge ports. With a fourvane pump running ve hundred revolutions per minute there are two-thousand of these inward and outward rushes of air per minute, causinga very disagreeable pulsatmg noise. When the pump is oil-sealed, as it`must be to prevent exces-v sive leakage and insure suflicientlubrication, there is always some oil being carried out with thedischarged air. The above mentioned pulsations tear this oil up andatomize it so thoroughly that it passes through any oil separator thatmay be provided and escapes in the form of a fog in the discharge,v

not waste oil'and will have la maximuml capacity and maximum eiiiciency.

I obtain maximum capacity by making the inlet ports of ample size and ofsuch length that each vane crosses the port ends at the insta-nt thatthe volume between it and the vane ahead is at a maximum. I obtain quietoperatlon, conservation of oil and high etliciency by making thedischarge ports of ample size and of such length that each vane crossesthe port ends at the instant that the pressure in the space behind it isabout equal to the pressure in the discharge passage.

, In the accompanying drawings, which show a pump embodying thisinvention in a preferred form:

Figure l is a section through the pump parallel to the shaft.

Fig. 2 is a section on line 2-2 of Fig. 1 at right angles to the shaft.

Fig..3 is a section on line 3 3 of Fig. 1, showing the Shape of the oilreservoir at the pulley end. l

The rotor a is mounted on a shaft b carried by bearings in the heads cand d. The rotor has four slots in which vanes or wings e slide towardand fromthe shaft. Spacers f maintain a uniform distance betweenopposite vanes. In the outer edges of the vanes e are'grooves in whichsemi-circular rods g Oscillate.

Between the having a bore of such shape that all diameters (or chords)measured through the cenheads Gand d is a housing bter of the shaft bare equal. At one Aside of the housing is an inlet chamber z' connectedwith the bore by the ports j' and at the other side is an outlet chamberk connected with the bore by the port Z.

The bottom end of the lower port j is so located that at the instant thetip g on the end of a vane e passes over and closes it, the spacebetween that lvane and the vane ahead of it isat a maximum.

The lower end of port Z is so located that i the tip g of a vane e willpass over it and open the port at theftime thatthe'pressures on the twosides of such vane are equahand at the time that the volume betweenthatsame ratio to the maximum volume that the inlet pressure dlvided by `itsabsolute temperature bears to the discharge pressure divided by thedischarge temperature.

From-the outlet chamber c a passage m leads to the central chamber ofthe oil separator,ithe upper half of which-is separated /from the sidechambers by the half partitions n and o. From the side chambers,

passages p lead to the exhaust pipe. Acrossv the bottom of thecentraLcharnber is a dividing fence g. From the side chamber of the oilseparator there lead to the shaft oil holes 1' and s having branches tand u communicating with the inside of the rotor a.

Formed within the heads c and d are oil reservoirs /v and 'wcommunicating with the inside of the rotor a by holes w and y havingtheir lower edges above the bottom of the inside of the rotor. One headd carries a hollow axle 10 around which the pulley 11 revolves onbearing rollers 12 and drives the shaft b through the liexible coupling13.

In order to have an easy running pump the rotor a is made slightlyshorter than the housing k, giving clearance between `it and the heads,and it is so located that there is an appreciable clearance between thetop of the rotorrand the top of the housing. The vanes e are made easyfits in their slots and the separators f are made so short that thevanes turn freely in the housing.V These clearances, while, desirablefor easy running, all tend to cause leakage.

When in operation, the pump should contain suiiicient oil to cause thelevel in the reservoirs 'v and w to reach about one-quarto the' shell ofthe rotor. Centrifugal force,

due to the rapid rotation of this oil, will prevent the entrance ofexcess oil. Cen-r trifugal force will alsokforce the oil into all theclearance spaces and so seal them. Oil

that passes outward between the rotor andv the heads and through theclearances at the Sides of the vanes will seal the ends 'and outer edgesof the wings. Any excess oil 1 reaching the spaces between the rotor andthe housing will be thrown, with the discharging air, outward throughvthe port Z into the lchamber 7c and then upward at high velocity throughthe passage m. Because of the circular path that the air is compelled totake in the `oilI separator, all

oil in appreciable sized, drops will be thrown against thewall andwillcollect in the bottom, while the air will pass under .the partitions'n`- and o, upward through the passages p and out `through the exhaustpipe. If the oilwere so finely divided yas to form a fog, some of itwould be carried around and out with the air; but by arrangf ing thedischarge port as hereinbefore dej scribed, with consequentavoidanceofpuly sations at the discharge, the atomization of l p `vre5wall of'v n oil is prevented and its waste avoided.

As the oil flows down .the back the separator, it will bey divided, bythe fence g, into two streams, one lflowing to each end of the separatorand thence downward through the holes 1' and s to lubricate thebearings. All oill in excess of thatv re- -quired for the bearings willflow through the holes t and u to the-interior of the rotor, l

"supply forces some out through thel hole 22 in the inner ange of thehub and it escapes into the reservoir fw.

When the pump stops, all the oil from the annulus inside the rotor, withall oil from the separator, falls to the bottom of the rotor and a largepart of it flows outward through the holes and y, to be stored in thereservoirs fu and lw untilneeded again.

If the pump stands idle for a long time,

much of the oil from the reservoirs lv and lw may leak past the rotorinto the bottom of the housing. yWhen the pump .is started, the firstturn will throw this oil up into the separator, whence it will flow,partly by the holes 7' and t and partly by the holes s and u', to the.insideof the rotor, ready to perform its sealing and lubricatingfunction.

With the described porting, the pump has a maximum capacity for itssize, the discharge isrelatively quietLand the oil sent out of the pumpwith the discharge will be insuch large drops that practically all of itwill be caught in the oil separator and re-v turned to the pump.

Certain novel features of the construction herein shown, particularlythe arrangement of oil reservoirs below the bearing and open to theatmosphere and adapted to\ catchv drips from the bearings and thepulleyhub,

to supply oil to form a sealingannulus within the rotor and to receive'011 without overi type designed for producin n gree of'exhaustion, thecom inatlon with a.

ters Patent is;`

flow when thepump stops, are not herein claimed, asthey are not myinvention, but form the sub'ect-matter of another application filed byeredith Leitch filed February 3, 1920, Serial No. l56014.

AHaving now fully described my invention, what I claim and desire toprotect by Let- 1. In a vacuum pump rotor and sliding vanes, of a bodyhaving'a discharge port extending through such arc of the body as to beopened by a vane passing over it at substantially the time that thepressures on the two `sides, of the vane are equal.

2. In a vacuum pump of the sliding vane type, `the combination with abody having an inlet and a discharge, a contained rotor and slidingvanes on the rotor, said rotor and vanes having appreciable clearances,of means to seal said clearances Wlth a body of oil, and means tominimize atomization of oil in the discharge, said means comprising vthepositioning of the port communlcating with the discharge so thatit Willbe uncovered by a-vane at the time that the pres- Qf the sliding van@ aspecific de- `sules on the two sides' ofthe vaneare substantially equal.

3'. In a' vacuum pump ofthesliding vane I type, the combination with abody having,

Y an inlet and a discharge, a contained rotor and sliding'vaneson therotor,`said.r0tor and Avanes having appreciable clearances, of .means toseal said clearances with a body of preventpulsationvof airvfsubst'antiall the same time that the volume between suc vane and `thevane in advance -thereof is at a maximum, said body having an outletport'so positioned as to 4be opened by a. vane passing over it at theltime that the pressures'on the two sides of the vane are .substantiallyequal.

In testimony of which invention, I have hereunto set my hand, atPoughkeepsie,

of Januar 1920.

N. Y., on this 29 da Y, ELDENv HALL;

